The present invention relates to the production of light by chemiluminescence and, more particularly, the use of specific fluorescent agents for this purpose.
The principle and the techniques for the production of chemiluminescent light are described in detail in
U.S. Pat. No. 4,678,608 which is incorporated in the present description as a reference.
Chemiluminescence is produced by a reaction in the liquid phase of an activator such as hydrogen peroxide with a fluorescent agent and an oxalate. Optionally, other secondary compounds can be present In general, they are also fluorescent agents, which modify the characteristics of the emitted light.
Until now, there exits no simple means to produce red chemiluminescent light which is satisfactory for the users, although there has been a report on the use of derivatives of naphthacenes and tetracenes as auxiliary fluorescent agents to produce red chemiluminescence Thus, U.S. Pat. No. 3,557,233 cites the use of 5,12-bis(phenylethynyl)naphthacene, pentacene and 6,13-bis(phenylethynyl)pentacene as a fluorescent agent to produce fluorescence at a wavelength of 578, 578 and 690 nanaometes, respectively. Nevertheless, these compounds were shown to be unstable in the reaction and the duration of the chemiluminescence obtained in this manner is too short to be of commercial interest.
However, on the market side, there exists a significant demand for red chemiluminescent light. Red is a color which is greatly appreciated by the public at large and, in addition, under several circumstances where chemiluminescence is applied for safety and rescue purposes, the color red is imperatively required because of traditions or conventions.
Because there is no commercially usable red chemiluminescent liquid, U.S. Pat. No. 4,379,320 has proposed a method which consists in using a non-red chemiluminescent liquid, whose luminosity is satisfactory both with regard to intensity as well as duration, and to use it in a container whose translucent walls are dyed in the composition by a red fluorescent dye. The claimed chemiluminescent liquid emits wavelength which is lower than that of the dye of the wall. Thus, the color is yellow is cited preferentially. Some articles based on this principle are in fact commercially available on a large scale; however, the drawback that is mentioned is that it produces a red-orange color and not a true pure red color, the latter could be designated as "signal red" with an emission which would be at a wavelength of approximately 625 nanometers.
It has now been observed unexpectedly that known fluorescent dyes which are soluble in organic solvents and, particularly, esters, can be used advantageously to produce a chemiluminescent light, particularly a red chemiluminescent light, which is particularly appreciated by the users and which differs from the colors produced in the prior art.